Devices used to warn approaching motorists of a hazardous condition are generally constructed in a manner to facilitate the rendering of visual signals over a complete field of 360 degrees. Consequently, such devices generally comprise a plurality of sealed beam lamps rotating about a vertical axis.
The utilization of such devices on heavy equipment, such as snow plows, road graders and the like, has generally resulted in severe problems due to reductions to normal life-expectancy. Experimentation has determined that these abnormally premature failures are caused by the mechanical exaggeration of electrical erosion at current carrying bearing or journal points. Normal applications of such devices use the rotating shaft of the device to carry current to the sealed beam bulbs. This results in an appreciable degree of arcing activity between the shaft and the journal bushings. In the presence of severe vibration loads, the constant motion serves to significantly amplify the arcing factor, giving rise to a spark-erosion condition. As the shaft rotates about its axis, circumferentially encompassed by the journal bushing, the effect of normal friction is grossly increased by the combined factors of increased shaft and journal temperatures and the erosion generated particles from the generally soft journal bushing. The direct result is the formation of an abrasive lapping compound which rapidly deteriorates the basic dimensional accuracies of fit initially established. As the clearance between the components increases, the arcing increases in severity and the factors causing failure are aggravated.
Therefore, the invention is directed to a rotating warning lamp wherein the lamp current does not pass through the shaft-journal interconnection and, preferably, the motor current also does not pass through the shaft-journal interconnection.